There are myriad videos on YouTube with advice about this.
Basically the advice they give is:- after you've checked the weather as recommended above, you lay out everything on the bed, sort it into things that match and work out enough outfits for the days you are there. For up to a week. I would take clean socks, tights, knickers etc for each day as these don't take up much room and you won't need to wash anything in that time. Very few trousers and skirts in neutral colours - perhaps as few as one of each..
A variety of tops, long- and short-sleeved for inside and outside, to be worn in layers. You don't need to wear different things each day. Don't make them all your best clothes as you will hopefully be given a chance to burp the baby and will be helping in the house.
Don't be surprised if the dress code isn't terribly formal for the ceremony - continentals don't dress up quite so much in my experience. If possible, ask your daughter/daughter-in-law what is expected.
Wear one pair of shoes for the journey - the most bulky ones, sturdy enough for walks with the pram. Finnish parents like their babies to spend a lot of time outdoors. Into your case go just one other pair of shoes (to go with your outfit) and some slippers.
Go back and check on what you have laid out and reduce the amount. Don't forget to put the clothes you are travelling in on one side.
And don't forget nightwear (this has happened to me before - concentrating so much on selection of daywear, I completely forgot about a nightie!)
Don't pack a sponge bag. At least, not a full one.Small bottles and pots of your toiletries and creams, well wrapped in small plastic bags to prevent leakage, will fit in the corners and gaps in your case. If you like, pack a sponge bag flat on top when you have finished, to carry your stuff to and from the bathroom. This, of course, only if you are checking your case in. Otherwise they go in your liquids bag.
There's no need to lumber yourself with a huge heavy case. Whittle it down.
Many of the YouTube videos show you the optimum way to fold or roll the clothes - there are endless differing opinions. The relentless debate about packing cubes - yay or nay - the different ways to "organise" things. It's all a bit over the top really.
Don't weigh yourself down with unnecessary stuff.
Have a lovely time, and come back and tell us about it afterwards. The idea of a secular "naming ceremony" sounds intriguing.
